The 71-year-old firebrand stormed to victory in Monday's election, securing an insurmountable lead of nearly six million votes over his nearest rival, as a growing global howl for strong, populist leaders swept across the Southeast Asian nation.

Mr Duterte, the longtime mayor of the southern city of Davao, captivated Filipinos with vows of brutal but quick solutions to crime and poverty, while offering himself as a decisive strongman capable of resolving a host of other deeply entrenched problems in society.

"It's with humility, extreme humility, that I accept this, the mandate of the people," Mr Duterte told AFP in Davao early on Tuesday morning as the results came in.

Market voices on:

In other comments to reporters who had converged on Davao, Mr Duterte offered an olive branch to his rivals following a deeply divisive campaign that had seen President Benigno Aquino brand him a dictator in the making who would bring terror to the nation.

"I want to reach out my hand and let us begin the healing now," said Mr Duterte, whose campaigning style and ability to upend conventional political wisdom have drawn comparisons with US Republican Donald Trump.

However, Mr Duterte vowed to push through on the central plank of his campaign platform - ending crime across the nation within six months and eliminating corruption.

On the campaign trail he had enraged critics but hypnotised fans with profanity-laced promises to kill tens of thousands of criminals, forget human rights laws and pardon himself for mass murder.

While avoiding such extreme inflammatory remarks, Mr Duterte said a law-and-order crackdown that particularly targeted drugs would be one of his top priorities when he became president, and he was prepared to kill.

"I will do it (fight drugs), even if they say I am an executioner," said Mr Duterte, who rights groups accuse of running vigilante death squads in Davao that have killed more than 1,000 people.

"Look what I did to Davao. I will not let down the people." Mr Duterte, who on the campaign trail boasted of being behind the death squads, also had a warning for corrupt police.

"If you are a policeman and stick to your racket, choose: either you kill me or I kill you," he said.

The election commission was not expected to officially proclaim Mr Duterte as the winner of Monday's vote for more than a week.

However it had authorised the PPCRV, a Catholic Church-run poll monitor, to tally the votes, and they showed on Tuesday morning with almost 90 per cent of the total counted that Mr Duterte could not lose.

Mr Duterte had 38.65 per cent of the vote, with administration candidate Mar Roxas on 23.16 per cent and Senator Grace Poe in third with 21.71 per cent, according to PPCRV.

In the Philippines, a winner is decided simply by whoever gets the most votes. The next president will be sworn in on June 30.

Ms Poe, the adopted daughter of movie stars, conceded just after midnight on Tuesday.

"I congratulate Mayor Rodrigo Duterte and pledge my support in working to heal our land and to unite our people toward the continued development of our country," Ms Poe told reporters in Manila.

Mr Roxas's aides said he would give a press conference on Tuesday afternoon, but refused to disclose whether he planned to concede.

Mr Duterte had during the campaign dominated local media coverage and generated international headlines with relentless gutter talk, including branding the pope a "son of a whore".

He also boasted repeatedly about his Viagra-fuelled affairs.

Mr Duterte caused further disgust in international diplomatic circles with a joke that he wanted to rape a "beautiful" Australian missionary who was killed in a 1989 Philippine prison riot.

Mr Duterte was enraged by the reaction to the rape comments, which included criticism from the US and Australian ambassadors, insisting they were taken out of context.

Despite all the rhetoric, analysts said Mr Duterte is expected to moderate his inflammatory comments from now on and unlikely to unleash a killing spree.

"Extrajudicial killings and forgetting human rights, he cannot do that because it will create more instability and chaos, which is what he wants to prevent," Earl Parreno, an analyst from the Manila-based Institute for Political and Economic Reform, told AFP.

"During the campaign he was stage acting, he was exaggerating to get across a message."